The present invention relates to an actuator suitable for an apparatus popularly known as a xe2x80x9cuniversal headxe2x80x9d, mainly for three-dimensionally positioning of a monitoring camera, a disco-lighting unit, an antenna drive unit, a (multi-axis multi-articular) robot, or the like, particularly to a rotary electric machine having a coaxial output hollow shaft with a reduction gear and a slip ring.
In such an apparatus called a universal head mainly for three-dimensionally positioning a monitoring camera, a disco-lighting unit, an antenna drive unit, a multi-axis (multi-articular) robot, or the like, a panning (horizontally rotating) motor and a tilting (vertically rotating) motor are used for three-dimensional positioning by an actuator. Usually the tilting motor is horizontally rotated by the panning motor, and a camera or a light attached to the tilting motor is positioned in a desired three-dimensional position.
According to the configuration of such a three-dimensionally positioning apparatus in the related art, power supply lead wires for the tilting motor or power supply cables for the camera or the light may be twisted or the camera or the light cannot be rotated continuously when the camera or the light is driven. Thus, for example, there is a demerit in that the camera or the light cannot be moved and rotated over a limited angle of about 300xc2x0.
Therefore, the present inventor has filed an application for a patent titled xe2x80x9cDirect Drive Electric Motor Apparatus Incorporating Slip Ring Assemblyxe2x80x9d as Japanese Patent Application No. 284695/1998, and thereafter submitted a translated document. A description is set forth below about this related-art direct drive apparatus with reference to FIG. 3.
A television camera apparatus 101 shown in FIG. 3 is constituted by a well-known dome-shaped camera enclosure 103 used in a monitoring system; a transparent or semi-transparent dome 103A; a base plate 104 which is fixedly attached to the upper portion of the camera enclosure 103; a panning motor 102 which is fixedly attached to the surface of the base plate 104; a camera holder bracket 107 attached to a rotor 114 of the panning motor 102 disposed so as to be rotatable around the horizontal axis H (pan) which extends through the center of the base plate 104 and which is orthogonal to the base plate 104; and a tilting motor 110 fixedly mounted on one side of the camera holder bracket 107 which is formed as an inverted U-shaped fork-like holder.
A television camera 112 is attached to a rotor 116 of the tilting motor 110, so that the camera 112 is mounted so as to be rotatable around the vertical axis V (i.e. tilt axis). On the opposite side, the camera 112 is mounted on the camera holder bracket 107 via a well known pivotally rotating joint 115 extended along the V axis.
The V axis (tilting axis) which is orthogonal to the H axis (panning axis), the L axis (lens) which is orthogonal to the V axis (tilt), and the H axis (panning axis) are made to intersect each other at the center of the dome-shaped cover portion 103A so as to provide the all-round unobstructed panning and tilting movement within the dome sphere.
The panning motor 102 incorporates rotary contacts or a slip ring assembly 106 inside its rotor 114.
The slip ring assembly 106 per se is a known assembly constituted by a rotating conductive metal ring, and a complementarily mounted conductive metal brush that applies pressure to the metal ring for holding a continuous current flow through the metal ring during the rotation of the metal ring.
Connecting wires 105 include wires for feeding power and control signals to the camera and wires for receiving a video signal, an audio signal and data signals from the camera. The connecting wires 105 pass through an opening in the domed closure or case 103 and the base plate 104 for connecting the rotating ring of the slip ring assembly 106.
Wires 113 for feeding power to the panning motor 102 may be fed through a separate opening 113A directly to the panning motor 102 if the panning motor 102 is an inner rotor type, or the wires 113 should be connected to the panning motor 102 along with the connecting wires 105 if the panning motor 102 is an outer rotor type.
Wires 108 connected at their one ends to the brush of the slip ring assembly 106 are fed through an opening in the holder bracket 107 and are connected at their other ends to the rotating ring of a slip ring assembly 109 mounted on a portion inside the shaft of the rotor 116 of the tilting motor 110. Wires 111 connected at their one ends to the brushes of the slip ring assembly 109 are connected at their other ends to the camera 112 and to a control circuit (not shown).
It is obvious from FIG. 3 that, in this arrangement, the camera can rotate endlessly around its panning H axis or its tilting V axis without causing the wires to flex or twist.
Furthermore, it is obvious that the camera holder bracket 107, which is mounted directly onto the rotor 114 of the panning motor 102, is directly driven by the drive motor without any power transmission mechanism.
Similarly, it is obvious from FIG. 3 that the rotor 116 of the tilting motor 110 can directly drive the camera tilting position without using any power transmission mechanism.
The elimination of the power transmission mechanism and assemblies reduces the size of the dome-shaped camera enclosure 103, simplifies the configuration, improves the efficiency and accuracy of the positioning device, and also improves the reliability.
Incidentally, specific configurations of the panning motor 102 and the tilting motor 110 are shown in detail in the specification and translated document of Japanese Patent Application No. 284695/1998 which is an application according to the above-mentioned related art.
As a result of investigation carried out after filing the application of the above-mentioned related art, however, it was found that there was a problem when a stepping motor suitable for positioning was used as the motor for direct driving without using any reduction gear. That is, it was difficult to start up if load inertia was large. Therefore, a large motor was required, so that the apparatus became unfavorably high in price and large in size in spite of no reduction gear.
It is therefore an object of the present invention to solve the foregoing problem, and to provide a rotary electric machine having a coaxial output hollow shaft with a reduction gear and a slip ring, which constitute an actuator optimum for and practical in use as a three-dimensionally positioning apparatus for a monitoring camera, a disco-lighting, an antenna, etc.
In order to attain the above object, according to a first aspect of the present invention, that is as defined in claim 1, there is provided an inner rotor type rotary electric machine having a coaxial output hollow shaft with a reduction gear and a slip ring, comprising: a hollow rotation shaft; a reduction gear for reducing an output of the inner rotor type rotary electric machine and extracting an output through a hollow shaft of the reduction gear coaxially with the hollow rotation shaft; and a slip ring provided in a hollow portion or an output portion of the reduction gear.
According to a second aspect of the present invention, that is as defined in claim 2, there is provided an outer rotor type rotary electric machine having a coaxial output hollow shaft with a reduction gear and a slip ring, comprising: a hollow rotation shaft; a reduction gear for reducing an output of the outer rotor type rotary electric machine and extracting an output through a hollow shaft of the reduction gear coaxially with the hollow rotation shaft; and a slip ring provided in a hollow portion or an output portion of the reduction gear.
According to the above-mentioned first or second aspect of the present invention, the rotary electric machine is a stepping motor.
According to the above-mentioned first or second aspect of the present invention, at least one of a position sensor and a speed sensor is provided in the hollow portion or the output portion of the reduction gear along with the slip ring.
According to a third aspect of the present invention, there is provided a driving device for performing three-dimensional positioning, comprising: a rotary electric machine having a coaxial output hollow shaft with a reduction gear and a slip ring; and means for performing giving and receiving electric power through the slip ring so that the driving device is driven.
According to the first or second aspect of the present invention, preferably, the reduction gear is a harmonic reduction gear constituted by an output gear which has internal gear teeth and an inner gear which is made of a flexible material and in gear with the output gear, the inner gear having gear teeth on an outer circumference thereof, the number of the gear teeth of the inner gear being set so as to be smaller than the internal gear teeth, an inner circumference of the inner gear being forced to form an ellipse so that the inner circumference of the inner gear is drawn by a longer axis of the ellipse to make the gear teeth of the inner gear comes to be in gear with the gear teeth of the output gear.
According to a fourth aspect of the present invention, there is provided a multi-axis positioning device which comprises: at least one rotary electric machine and means for performing giving and receiving electric power through the slip ring so that the multi-axis positioning device is driven. In this case, another panning motor is attached to an output portion of a panning motor to perform multi-axis positioning. In this case, a horizontally moving multi-axis is realized in which a tilting motor is not always required. That is, there is provided a two dimensional positioning.
In such a configuration, load inertia J, which is converted into the motor rotation axis, can be reduced to:
J=JL/N2
where N designates the reduction ratio and JL designates the load inertia before conversion.
In addition, because the reduction gear is a coaxial type, a hollow portion can be provided at the center of the reduction gear coaxially with the hollow rotation shaft of the motor. Accordingly, if a slip ring is provided in a reduced final output portion, power can be supplied from the static side of a non-output-side center hole of the motor or the like, so that the output of the slip ring can make motion uniform with the reduction gear output portion. As a result, there is no fear that the lead wires of the tilting motor or the like are twisted as described above. Thus, every rotating portion can make continuous forward rotation or continuous backward rotation over 360xc2x0.